Fluid pump

ABSTRACT

The invention relates to an electric fluid pump with a semi-axial construction, wherein the pump housing ( 32, 33, 34 ) has at least two identical pump housing parts ( 33, 34 ). This feature of the invention reduces the number of different components required to manufacture the electric fluid pump and thus reduces costs while achieving a high operating efficiency.

This is a National Phase Application in the United States of International Patent Application No. PCT/EP2006/009762 filed Oct. 10, 2006, which claims priority on German Patent Application No. 10 2005 054 060.0, filed Nov. 10, 2005. The entire disclosures of the above patent applications are hereby incorporated by reference.

FIELD OF THE INVENTION

The invention is directed to a fluid pump for internal combustion engines, comprising an electric motor with a rotor arranged in a motor housing and a stator, the rotor being arranged on a drive shaft at least in a manner secured against rotation, an impeller fastened on the drive shaft, at least one set of guide vanes arranged behind the impeller in the flow direction of the fluid to be conveyed, and a pump housing enclosing the motor housing, the impeller and the guide vanes and at which a pressure port and an intake port are arranged opposite the axial ends.

BACKGROUND OF THE INVENTION

Fluid pumps for internal combustion engines are used especially as coolant pumps in the cooling circuit. Whereas, in the past, a direct coupling with the engine speed existed and the pumps were driven by belt or chain drives, more recent engines increasingly use electric variable speed coolant pumps with a can, so as to realize a modern thermal management. Thus, an excessive delivery rate can be prevented, so that, for example, the internal combustion engine can be heated up faster after a cold start. The delivery rate can be controlled according to the actually required cooling capacity.

Such a pump is known, for example, from MTZ No. 11, vol. 2005 (p. 872-877). This electric coolant pump comprises an EC motor as the drive unit and has a pump head with an axial inlet and a tangential outlet. The components and especially the housing parts used therein are rather large for the power input of the pump, since a relatively large drive motor has to be used.

Thus, US 2002/0106290 A1 discloses an electric fluid pump of semi-axial construction, whereby, with the same power input to the electric motor, the electric motor can be made smaller to obtain higher speeds, so that the same delivery rate can be obtained with a more compact structure. It comprises a completely enclosed electromotor with a guide vanes provided at the outer side thereof. However, behind the guide vanes, seen in the flow direction, obstacles are formed that hinder the establishing of the electric contacting to the electronic unit.

On the impeller side, the entire motor is sealed with gaskets from the environment. It is at least debatable whether such a sealing at the rotating parts is sufficient.

The pump housing is bipartite and has various steps and through holes for electric contacting. Depending on the desired maximum delivery rate, different electric motors and housings must be designed. Likely, a completely irrotational flow is not achieved due to the rather short guide vanes. Further, the pressure loss due to the passages of the electric contacts is rather high so that the gain in the power input of the electric motor is partly thwarted by the pressure losses occurring.

Due to the relative arrangement of the housings, the same have to be manufactured with high production accuracy, they have to be reconfigured for higher delivery rates and have to be mounted in a troublesome manner. No provisions are made to prevent errors upon mounting.

In addition, radial and axial pumps are known from EP 0 566 087 A1 and DE 202 01 183 U1, wherein the suction and pressure ports are made from identical housing parts. However, these cause high pressure losses and thus a low efficiency.

Therefore, it is an object of the invention to configure especially the pump housing such that production flaws can be compensated, a reduced number of different components is obtained and assembly errors are minimized, while at the same time a high efficiency of the pump is to be achieved.

SUMMARY OF THE INVENTION

This object is achieved with the characterizing part of the main claim. Thereby, the number of different components and thus the costs are reduced, while a high efficiency is to be realized. Moreover, the connection with a suction-side and a pressure-side pump housing part is simple to make, and little loss occurs. Thus, intake and pressure ports can be integrated in these parts. Further, these are the largest and therefore most expensive parts in the production. Notably, tooling costs are saved. Assembly errors caused by confusing the mounting direction are excluded. The shape of the individual ports facilitates the connection to the axially adjacent housing parts and provides for a steady low-loss transition when the flow is deflected. Mounting into a cooling system is readily realized because of the axial position of the suction port with respect to the pressure port in the cooling system. The package size, given a certain motor size to be used, is minimized. Further, no long inflow channel exists and a good efficiency is achieved due to the semi-axial blading. No additional space for the impeller is required. Thus, only a small mounting space is required. High production accuracies are not required.

In a particular embodiment, the set of guide vanes is arranged in a cylindrical pump housing part arranged axially between the two identical pump housing parts. This simplifies the shape and thus the production of the identical pump housing parts, since no direct abutment of the inner surfaces at the necessary guide vanes is required. Thus, the production accuracy can be reduced.

Accordingly, a fluid pump is provided which has a small number of different components, is adapted to be mounted in a simple manner and with little probability of error, and, due to the identical construction of the pump housing parts, reduces tooling and production costs especially with small quantities.

An embodiment of the invention is illustrated in the drawing and will be detailed hereinafter.

BRIEF SUMMARY OF THE DRAWING

The FIGURE is a side elevational sectional view of a fluid pump according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The fluid pump illustrated in the FIGURE, which is particularly suited as a coolant pump in internal combustion engines, is driven by an electronically commuted electric motor 1, formed by a stator 2 and a rotor 4 arranged on a drive shaft 3. The axial end of the drive shaft 3 is provided with an impeller 5 that is realized in a semi-axial construction and by whose rotation the fluid to be conveyed, especially a coolant, is conveyed substantially axially from an intake port 6 through the fluid pump to a pressure port 7.

The electric motor 1 is arranged in a motor housing formed by a first, suction-side motor housing part 8 and a second, pressure-side motor housing part 9. The drive shaft 3, on which the impeller 5 is arranged, is passed through the suction-side motor housing part 8. For this purpose, the suction-side motor housing part 8 has a bore 10 with a first bearing 11 being arranged therein for supporting the drive shaft 3. Behind the first bearing 11, seen from the suction side, an ceramic axial sliding bearing 12 as well as a rubber sleeve 13 and a spacer 14 are situated. This assembly allows to achieve a sufficiently vibration-damped support of the impeller side of the drive shaft 3 of the electric motor 1. The spacer serves to widen the distance between the first bearing 11 and a second bearing 15, whereby an angular error caused when making the bore 10 for receiving the bearings can be compensated better.

Further, behind the spacer 14, a rotor pack 16 is arranged on the shaft, comprising axially extending slits for receiving magnets 17 corresponding with a stator coil 18 in a manner known per se. The rotor 4 is delimited axially and radially by an enclosure 19. The stator coil 18 is wound on an insulating body 20 and axially delimits a stator pack 21 in a manner known per se. To close the magnetic circuit, this stator pack 21 is positively connected with a magnetic yoke 22. This magnetic yoke 22 rests against an abutment 23 formed on an inner surface of the first suction-side motor housing part 8.

The rotor 4 is separated from the stator 2 by a can 24 resting on the suction side of the pump in a corresponding receiving opening 25 of the suction-side motor housing part 8, and whose opposite axial end is arranged, in turn, in a corresponding receiving opening 26 of the pressure-side motor housing part 9. The stator 2 with its sensitive coil 18 is thus situated in a dry space separated by the two motor housing parts 8 and 9 and the can 24.

Provided at the pressure-side end of the can 24 is a closure member 27 in which the second bearing 15 is arranged to support the drive shaft 3. This closure member 27 is secured axially by the pressure-side motor housing part 9, which, with the interposition of a gasket 28, is arranged in a receiving opening 29 of the suction-side motor housing part 8.

The stator coil 18 is contacted, via a bore 30, in the radial direction through the pressure-side motor housing part 9. To prevent flow losses caused by such additional built-in means, this bore is made through supporting ribs 31, as known in prior art, which ribs are required to provide a pump housing with sufficient strength and for mounting the same. For this purpose, the supporting ribs 31 are sufficiently wide and are shaped similar to an airfoil, so that no constriction of the cross section is formed. Thus, an electric contact element, not illustrated, can be passed through the bore 30 to an electronic unit (also not illustrated) for controlling the motor 1.

In the embodiment illustrated, the supporting ribs 31 are formed such that they simultaneously serve as the guide vanes, so that no additional guide vanes is needed immediately behind the impeller 5. This allows for a simple manufacturing of the suction-side motor housing 8 as one piece, with the supporting ribs and a cylindrical radially outer pump housing part 32. This pump housing part 32 encloses the radially inner motor housing part 8, as well as the entire electric motor 1.

On the downstream and the upstream side of the housing part 8, 31, 32, two respective identical pump housing parts 33, 34 are fastened by a screw connection, with a gasket 50 interposed therebetween. The suction-side pump-housing part 33, flaring in the direction of flow, comprises the intake port 6 configured as a cylindrical section 35, as well as an adjoining flaring section 46. The semi-axial impeller 5 of the fluid pump is arranged in the transition 37 between the first section 35 and the second section 36. In the present embodiment, the flaring section 36 is adjoined by another short cylindrical section 38 of larger diameter to achieve a smooth transition to the cylindrical pump housing part 32.

Corresponding sections tapering in the direction of flow and cylindrical sections are also provided at the pressure-side pump housing part 34, the same reference numerals being used because of the identity of the parts.

Moreover, the identical pump housing parts 33, 34 are formed with grooves 39 into which radial ends 40 of recirculation vanes 41 engage. These recirculation vanes 41 serve as the conducting device 42 by means of which a completely irrotational flow is obtained behind the pressure port 7. This conducting device 42 is formed on a surface 43 of the pressure-side motor housing part 9 and becomes necessary, because the supporting ribs 31 serving as guide vanes are made rather short and a completely irrotational flow is usually not achieved in this part of the fluid pump. Moreover, the pressure-side motor housing part 9 can be made of plastic material, whereas the suction-side motor housing part should possible be made of aluminum and is thus more expensive. Such a configuration of the guide vanes in this portion would require a rather expensive production method, whereas the conduction device at the plastic housing part 9 is simple and economic to manufacture.

The grooves 39 also define the position of the pressure-side pump housing part 34 with respect to the pressure-side motor housing part 9. When the pump is assembled and the screws are tightened to fasten the pressure-side pump housing part 34 to the cylindrical pump housing part 32, the pressure-side pump housing part 34, by the recirculation vanes 40, presses the motor housing part 9 against the motor housing part 8 or into the receiving openings 29 of the motor housing part 8. Further, the motor housing part 9 is thereby pressed against the closure member 27 and the can 24, respectively, so that no additional fastening of the two motor housing parts 8, 9 is required.

When the pump is running, the rotation of the impeller 5 formed by a plurality of impeller vanes 44 conveys the fluid to be conveyed, in particular the coolant, through the space between the pump housing 32, 33, 34 and the motor housing 8 and 9, the fluid flows past the supporting ribs 31, where a part of the flow rotation is already removed due to their function as guide vanes, and it flows on through the conduction device 42 where the still existing rotation of the flow is removed completely so that the energy spent is converted as completely as possible into pressure energy and thus into an axial flow without incurring high friction losses.

Behind the impeller 5, a part of the fluid flows through bores 45 formed in the suction-side motor housing part 8. Another part of the fluid also flows behind the impeller 5 to the drive shaft 3, where it flows through between the first bearing 11 and the drive shaft 3, so that the sliding bearing present is sufficiently lubricated. Thus, cooling liquid is in the rotor space, which is conveyed further between the drive shaft 3 and the second bearing 16, as well as through non-illustrated bores in the closure member 27 and into a space 46 behind the same. This space 46 is connected with the space behind the same via another bore 47 extending axially through the pressure-side motor housing part 9. Thus, both a lubrication of the bearings 11, 15 and a possibility for cooling and discharging possibly existing volumes of air in the rotor space are obtained.

This semi-axial pump is especially characterized in that it can be of a particularly compact structure, since with the same power input the same delivery rate can be obtained though with a smaller motor size and an increased speed when compared with known pumps. This is achieved especially by the extremely reduced pressure losses in such a design, but also by the semi-axial construction.

Moreover, such a pump can be produced very economically, since fewer differently designed components exist. At the same time, this reduces the occurrence of possible errors during assembly. By omitting the additional set of guide vanes and by integrating the electric contacting in the supporting ribs, additional components are avoided and pressure losses are reduced. Thus, on the whole, a higher efficiency is achieved.

Because of the simplicity of the pump housing parts 33, 34, it is of course also possible to provide the same with a flange situated at the pressure port or the intake port, respectively. This allows both a direct connection to a motor housing and to connect a plurality of pumps in series to increase the fluid volume flow conveyed. This becomes possible especially by the fact that the conduction device 42 creates an irrotational flow so that the impeller 5 of a downstream pump could be flown to directly without incurring energy losses. Therefore, when twice the delivery rate of a pump is required, it is not necessary to build a larger pump with a corresponding larger motor, but, due to the identity of the components, one may simply connect the corresponding required number of pumps in series.

It is also conceivable, due to the simplicity of the suction-side pump housing part 33, in particular, to form the same integrally with valve housing parts so that the pump housing parts 33 could comprise a receptacle for a bypass or an integrated heat valve. Parts of the housing of an annular slide valve could also be made integrally with the suction-side pump housing part 33.

It should be noted that the embodiment illustrated merely is a possible embodiment of the invention, whose structure may be altered in several respects without leaving the scope of protection of the claims. 

1. A fluid pump for internal combustion engines, comprising: an electric motor with a rotor arranged in a motor housing and a stator, wherein the rotor is arranged on a drive shaft at least in a manner secured against rotation; an impeller fastened on the drive shaft; at least one set of guide vanes arranged behind the impeller in a flow direction of fluid to be conveyed; and a pump housing enclosing the motor housing, the impeller and the guide vanes, and a pressure port and an intake port are arranged opposite axial ends of the pump housing, wherein the fluid pump is configured as a semi-axial pump, and wherein the pump housing comprises at least two identical pump housing parts, one of which is a suction-side pump housing part and the other one is a pressure-side pump housing part, and the identical pump housing parts each comprise a first cylindrical section serving as an intake or pressure port, respectively, and that is adjoined by a flaring section terminating in a second cylindrical section of larger diameter, and the impeller of the fluid pump is arranged in the suction-side pump housing part in a transition portion between the first cylindrical section and the flaring section.
 2. The fluid pump for internal combustion engines of claim 1, wherein the guide vanes are arranged in a cylindrical pump housing part situated axially between the two identical pump housing parts. 